In steering systems, in particular in power-assisted steering systems, in which manual steering is assisted by an electric motor, an exact, reliable and permanent detection of a relative torque between an input shaft and an output shaft is particularly important for ascertaining the steering requirement. The torque measurement device used for detection is in this case generally installed between an input shaft, which is connected to a steering spindle connection, and an output shaft, which is connected to a pinion. The torque measurement device thus detects the relative torque between the steering spindle connection or input shaft and the pinion or output shaft and controls the drive of an electric motor via an electronic module. The electric motor may in this case serve for the power assistance of the conventional steering apparatus.
As regards the operating principle of a rack-and-pinion power-assisted steering system, reference is made, in this regard, to European Published Patent Application No. 0 366 691.
A method, conventional from practice, for fastening a torque measurement device to an input shaft and an output shaft of a steering system provides, in this context, for the torque measurement device to be welded to the input shaft and the output shaft. It became clear in this case, however, that this welded joint is complicated and not sufficiently reliable. A break of the weld seam may occur, for example, when the wrong material is welded. Since the torque measurement device is a safety-relevant element which is to operate with high precision and reliably, the fastening method must satisfy particularly stringent demands and possibilities of error must be ruled out as far as possible.
It is an aspect of the present invention to overcome disadvantages of the prior art, in particular to provide a method of the type initially mentioned, which allows an accurate, reliable and permanent fastening of a torque measurement device between an input shaft and an output shaft of a steering system and may be performed in a favorable and simple manner and which may largely rule out error sources which may lead to a release of the connection.